2nd Year Maintenance and Discontinuation of Imipramine in Panic Disorder With Agoraphobia

Background: The results from our 1 year placebo-controlled maintenance/discontinuation study in remitted panic disorder with agoraphobia patients confirmed the significant prophylactic effectiveness of imipramine maintenance treatment but suggested that this may be necessary in only 37% of the patients who relapse following discontinuation of 6 months acute imipramine treatment. This paper presents pilot data from a second year extension of the above-mentioned study with the aim of exploring the putative protective effects of maintenance imipramine therapy beyond the 1st year. Method: Eighteen patients from the 30 who survived, in stable remission, the first 12 months of the maintenance/discontinuation study gave written consent to participate in a double-blind 2nd year extension phase with the knowledge that those on placebo will continue on the same condition (N = 7, PBO–PBO) and those on imipramine (N = 11) will be rerandomized to 2nd year maintenance (N = 4, IMI–IMI) or placebo substitution (N = 7, IMI–PBO). The procedures continued unchanged from that of the 1st year of the study and patients were followed with planned assessments every 2 months over the second 12-month experimental period of the study. Results: None of the IMI–IMI patients relapsed, two (28.5%) of the IMI–PBO patients relapsed, and two (28.5%) of PBO–PBO patients relapsed. The mean estimated time without relapse was 10 months and 9 months for IMI–PBO and PBO–PBO, respectively. The estimated probability of not relapsing was .64 for IMI–PBO and .60 for PBO–PBO (Mantel-cox test χ 1 2 = .84, p = .77). Conclusion: These interlocking controlled observations tentatively suggest that a substantial degree of prophylactic efficacy continues and that a substantial need for continued prophylaxis exists beyond the 1st year of maintenance imipramine treatment in panic disorder with agoraphobia patients.